1. Field of the Invention
The present invention relates an apparatus and a method for lapping magnetic heads, and in particular to an apparatus and a method for lapping a workpiece provided with a plurality of magnetic heads.
2. Description of the Related Art
Conventionally, a thin film magnetic head, which is used in a disc drive in a computer, is manufactured in a batch process. In this process, a workpiece, provided with a ceramic bar (thereafter being divided into sliders) on which a row of transducers including a plurality of thin film magnetic heads are arranged, is lapped such that throat heights in gaps of the respective transducers are adjusted to have desired values at which optimum data signal processing can be realized.
A problem that exists in lapping such magnetic heads so as to obtain desired throat heights is that the ceramic bar or the workpiece is stressed and/or has an undesirable curvature or bow. Namely, when the ceramic bar is stressed and/or has an undesirable curvature or bow, a lapping apparatus can not uniformly lap the ceramic bar. For example, even if the throat heights of the magnetic heads on a center of the ceramic bar have optimum values, the throat heights of the magnetic heads on both ends of the ceramic bar might be too low or too high to have optimum values.
An apparatus for lapping magnetic heads, which can solve such problem, is disclosed in U.S. Pat. No. 5,620,356. The apparatus adjusts throat heights of thin film magnetic heads arranged on a ceramic bar to be optimum by correcting the curvature of the ceramic bar and lapping the corrected ceramic bar while measuring resistances whose values are changed by the throat heights.
In the lapping apparatus disclosed in the U.S. Patent, a workpiece, which is provided with a ceramic bar on which a row of transducers including a plurality of magnetic thin films are arranged, is adhered to a bottom of a tool which likes a long thin plate, and the tool is attached to a back plate of the apparatus. However, the conventional apparatus has a problem that an attitude of the back plate to which the tool is adhered is not based on the abrasive surface of a rotary lapping table. For example, let us assume a case that the back plate is set vertically based on the abrasive surface of the rotary lapping table which is set horizontally. In this case, if the abrasive surface of the lapping table is not set horizontally, the workpiece can not be lapped with accuracy, or flatness of the lapped workpiece is decreased. As a result, the throat heights of the magnetic heads become uneven.
Further, the conventional lapping apparatus is provided with three magnetic actuators which are used to correct the curvature or bow of the ceramic bar. However, since the magnetic actuators are operated to rotate arms and to supply operating forces to the workpiece through the pivotal movements of the arms, thrust characteristics of the magnetic actuators for rotating the arm are undesirably decreased.